Note 11 - Net Income Per Share - Net Income Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 164,375	$ 108,839	$ 105,268
Weighted-average outstanding shares - basic (in shares)	44,840	43,165	42,247
Effect of dilutive securities (in shares)	2,174	2,598	2,355
Weighted-average outstanding shares - diluted (in shares)	47,014	45,763	44,602
Earnings per share, basic (in dollars per share)	$ 3.67	$ 2.52	$ 2.49
Earnings per share, diluted (in dollars per share)	$ 3.50	$ 2.38	$ 2.36